Piston for a compressor, compressor, and method and removal tool for disassembling a piston

This application is the U.S. national phase of PCT Application No. PCT/EP2023/053264 filed on Feb. 10, 2023, which claims priority to EP patent application Ser. No. 22/156,037.8 filed on Feb. 10, 2022, the disclosures of which are incorporated in their entirety by reference herein.

The invention relates to a piston for a compressor, a compressor, in particular a high-pressure compressor with such a piston, as well as a withdrawal tool and a method for disassembling the piston.

High-pressure reciprocating compressors are often used to compress gases such as methane or hydrogen to a pressure between 100 bar and 1000 bar. Piston compressors typically have a piston guided in a cylinder between a top dead center and a bottom dead center. The piston typically comprises a piston rod and a plurality of piston rings that are attached to an outer circumference of the piston rod. The piston rings can, for example, have carrier rings, wherein sealing elements are attached to the carrier rings. The sealing elements are used to seal a compression chamber defined by the piston and the cylinder and, optionally, to meter a quantity of lubricant between the cylinder and the piston.

The piston rings are wearing parts that need to be replaced after a certain period of time. Depending on the design of the piston, replacing the piston rings may require complete disassembly of the piston and is therefore often time-consuming. Furthermore, space may be tight at the compressor's operational site, which makes replacement even more difficult.

JP 2003 206860 A describes a piston compressor for compressing gas, which has a piston with a piston rod and piston ring devices mounted on it. The piston ring devices each have a carrier ring with an L-shaped cross-section and a sealing element which is fixed to the carrier ring. To make it easier to replace the sealing elements, these are split in the circumferential direction so that they can be removed from the carrier ring without removing the carrier ring from the piston rod.

The problem of the invention is to find solutions which facilitate the replacement of sealing elements of a compressor piston.

This problem is solved by the subject-matter of the independent claims, respectively. Advantageous embodiments and further developments are the subject of the dependent claims referring back to the independent claims, as well as of the following description and the figures.

According to a first aspect of the invention, a piston for a compressor is provided. The piston according to the invention comprises a piston rod, which defines a longitudinal axis, and a piston ring package with a carrier sleeve extending along the longitudinal axis, which is arranged on a circumferential surface of the piston rod and is releasably fastened to the piston rod, and a plurality of piston ring devices arranged next to one another along the longitudinal axis, which are arranged on an outer circumferential surface of the carrier sleeve and are fastened to the carrier sleeve, the carrier sleeve preferably having a mechanical interface for attaching a withdrawal tool for applying a force directed along the longitudinal axis.

According to a second aspect of the invention, a compressor, in particular a high-pressure compressor for compressing gases, such as natural gas, methane or hydrogen, is provided with a piston according to the first aspect of the invention. The compressor can, for example, be set up to compress gas, for example to a pressure in a range between 100 bar and 1000 bar, in particular in a range between 100 bar and 300 bar. For example, the piston can be mounted in a cylinder such that it can move linearly between two dead centers.

According to a third aspect of the invention, there is provided a withdrawal tool for disassembling a piston according to the first aspect of the invention. The withdrawal tool comprises a coupling device for attachment to the preferred mechanical interface of the carrier sleeve and a pulling device for applying a force directed along the longitudinal axis to the coupling device.

According to a fourth aspect of the invention, there is provided a method for disassembling a piston according to the first aspect of the invention. In the method, a withdrawal tool is connected to the preferred mechanical interface of the carrier sleeve of the piston ring package, and the piston ring package as a whole is withdrawn from the piston rod by applying a force directed along the longitudinal axis to the carrier sleeve by means of the withdrawal tool. For example, the withdrawal tool according to the third aspect of the invention can be used to carry out the method.

One idea underlying the invention is to pre-assemble the piston rings, also referred to herein as piston ring devices, on a carrier sleeve to form a piston ring package or cartridge, and to fix this package to the piston rod as a pre-assembled unit. This means that a large number of piston rings are pre-assembled on the outer circumferential surface of the carrier sleeve, and the carrier sleeve is pushed onto an outer circumferential surface of the piston rod or the piston rod is passed through the carrier sleeve. The carrier sleeve preferably also has a mechanical interface or connecting structure to which a withdrawal tool can be fixed in order to apply an axial force to the carrier sleeve to disassemble the piston ring package. This allows the piston rings to be easily withdrawn from the piston rod together with the carrier sleeve.

One advantage of the invention is that the carrier sleeve and piston rings can be withdrawn from the piston rod together as a whole, as the piston rings are attached to the carrier sleeve and not directly to the outer circumference of the piston rod. The preferred mechanical interface further simplifies the withdrawal of the carrier sleeve from the piston rod. This simplifies the disassembly of the piston rings as well as the months of new piston rings and thus the simultaneous replacement of all piston rings.

A further advantage of the pre-assembled piston ring package is that it can be manufactured with high precision, that it can be configured and, if necessary, tested at a production site, and that this reduces the effort required to assemble the piston ring package and to center and fit the piston rings when replacing the piston ring package at the compressor's operational site, e.g. on a transport ship, a drilling platform or the like.

According to some embodiments, it may be provided that the carrier sleeve is frictionally attached to the circumferential surface of the piston rod. Accordingly, an inner circumferential surface of the carrier sleeve can be frictionally connected to the circumferential surface of the piston rod, at least in some areas, or rest against the circumferential surface. This achieves a reliable axial fixation of the carrier sleeve. Optionally, the carrier sleeve can also be axially secured by a securing element screwed to the piston rod.

According to some embodiments, the preferred mechanical interface can be formed by a thread. This offers the advantage of facilitating the connection of the withdrawal tool to the carrier sleeve.

According to an exemplary embodiment, an inner circumferential surface of the carrier sleeve can rest on a first axial section of the circumferential surface of the piston rod in a first end region of the carrier sleeve, and the thread can be formed as an internal thread on the inner circumferential surface at a second end region of the carrier sleeve located opposite the first end region in relation to the longitudinal axis, wherein the inner circumferential surface in the second end region of the carrier sleeve is located at a distance from a second axial section of the circumferential surface of the piston rod in a radial direction perpendicular to the longitudinal axis. The piston rod can thus taper from a first end region of the carrier sleeve towards a second end region of the carrier sleeve, e.g. at a step or a transition cone, so that an annular gap is formed between the internal thread provided in the second end region of the carrier sleeve and the outer circumference of the piston rod, into which the withdrawal tool can be inserted. This makes it even easier to remove the piston ring package. Furthermore, the internal thread offers the advantage that the space required for the preferred mechanical interface is kept to a minimum.

According to some embodiments, it may be provided that the carrier sleeve has a sleeve body and a collar projecting radially from an axial end of the sleeve body, with a piston ring device that is last in relation to the longitudinal axis resting against the collar. In this way, the individual piston rings can be fixed very easily in the axial direction. The axial end at which the collar protrudes in the radial direction can, for example, form the end of the first end region of the carrier body, which optionally rests on the circumferential surface of the piston rod. In other words, the collar is preferably arranged opposite to the preferred mechanical interface, which in turn is advantageously also arranged in an end region of the carrier sleeve.

Optionally, the collar can rest against a shoulder of the piston rod. This is a simple way of axially securing the piston ring package to the piston rod.

According to some embodiments, the piston ring devices can be connected to each other along the longitudinal axis. Accordingly, piston ring devices are advantageously fixed to the carrier sleeve in the axial direction.

According to an exemplary embodiment, it may be provided that the piston ring package has a first end piece and a second end piece, with the piston ring devices being clamped between the first and second end pieces. This provides a simple way of fixing all piston rings relative to each other in the axial direction.

According to some embodiments, each of the piston ring devices clamped between the first and second end pieces may have a through hole, and a threaded rod connecting the first and second end pieces may extend through the through holes. For example, the threaded rod may be screwed to a thread provided on the second end piece, and the first end piece may be secured to the threaded rod via a nut. The threaded rod offers the advantage that the clamping forces can be precisely adjusted in the axial direction. Furthermore, centering of the piston rings can be simplified in this way.

Optionally, the first end piece can be formed by a ring element and the second end piece by another piston ring device. This advantageously reduces the number of components in the piston ring package, as the second end piece performs both the function of a piston ring and the function of fixing the other piston rings.

According to some embodiments, it may be provided that the piston ring devices each have a carrier ring surrounding the outer circumferential surface of the carrier sleeve and a sealing element which is attached to the carrier ring.

According to some embodiments of the withdrawal tool, it may be provided that the coupling device has a sleeve, in which an end region of the piston rod can be accommodated and which can be coupled to the preferred mechanical interface of the carrier sleeve, and an end plate connected to the sleeve, which has a through hole with an internal thread, wherein the withdrawal device has a threaded rod which can be screwed into the internal thread of the end plate in order to be supported against an axial end of the piston rod. The sleeve of the withdrawal tool can, for example, have an external thread which can be screwed to a mechanical interface of the carrier sleeve designed as an internal thread. To remove the carrier sleeve, for example in the process described above, the threaded rod of the withdrawal tool is screwed into the internal thread of the end plate of the sleeve and thus presses against the axial end of the piston rod. The reaction force directed away from the piston rod along the longitudinal axis is transferred to the sleeve via the internal thread of the end plate and from this to the carrier sleeve, so that the carrier sleeve can be easily pulled off the piston rod.

The features and advantages disclosed for one aspect of the invention are also disclosed for the respective other aspects.

Generally, identical parts are marked with identical reference symbols in the drawings, unless otherwise indicated.

shows an exemplary perspective view of a pistonfor a compressor (not shown). In particular, the compressor can be a high-pressure piston compressor which is set up to compress gases, such as natural gas, methane, hydrogen, etc., in particular to a pressure in a range between 100 bar and 500 bar. For example, the compressor can be used on a transport ship or a drilling platform, e.g. to compress gas that accumulates in a storage tank due to vaporization from the liquid phase and feed it to an internal combustion engine. Piston, which is described in detail below, can be moved in a horizontal or vertical arrangement by a crankshaft alternately between two opposing dead centers. The pistoncan be guided in a cylinder (not shown). Optionally, the pistoncan be designed as a double-acting piston and perform compression work both when moving in a first direction and when moving in the opposite direction.

As illustratively shown in, the pistoncan have a piston rodand a piston ring package. Furthermore, the pistoncan have a piston top sectionand/or an axial lock.

shows a partial sectional view of the pistonshown in. As shown in, the piston rodcan, for example, be realized as a shaft with a circular cross-section. In general, the piston roddefines a longitudinal axis L, which is enclosed by a circumferential surfaceof the piston rod. As shown in, the piston rodcan have a first axial sectiondesigned as a centering section with a first diameter and an expansion sectionlocated at a distance from this along the longitudinal axis L with a second diameter that is smaller than the first diameter. As illustratively shown in, the first axial sectionand the expansion sectioncan be connected to one another by a first conical section. An end sectionof the piston rod, which ends at an end faceof the piston rod, has a third diameter. The third diameter can, as illustratively shown in, be essentially the same as the first diameter. In this case, the expansion sectioncan, for example, be connected to the end sectionby a second conical section, as shown as an example in, or by a shoulder. However, it is also conceivable that the third diameter is equal to the second diameter or generally smaller than the first diameter.

Optionally, the end sectionof the piston rodcan have an external thread, as also illustratively shown in. Also optionally, the piston rodcan have a shoulder, designed as a piston crown, which is arranged at a distance from the end faceof the piston rodand projects in a radial direction R running perpendicular to the longitudinal axis L. For example, the shouldercan be arranged directly adjacent to the first axial sectionin relation to the longitudinal axis L, in particular in such a way that the first axial sectionis located between the end faceand the shoulder, as illustratively shown in.

In particular, the piston rodcan be made of a metal material, such as a high-strength structural steel.

As shown inand with more details in, the piston ring packagecan comprise a carrier sleeveand a plurality of piston ring devices, each comprising a piston ringand a chamber ring. Optionally, the piston ring packagecan also comprise a first end piece, for example designed as the last chamber ring, and a second end piece, for example designed as a cover ring, as shown as an example in. Also optionally, the piston ring packagefurther comprises one or more threaded rods, as illustratively shown in, which hold together the piston ring devicescomprising piston ringsand chamber rings, the first end pieceand the second end piece. As shown in, in possible embodiments a piston ringcan consist of a single part or of a plurality of partial rings,.shows piston ring devicesarranged towards the first end regionof the carrier sleevecomprising a chamber ringand in each case a single piston ring, whereas the piston ring devicesarranged towards the second end regioncomprise a chamber ringand in each case a piston ringconsisting of a first piston ring partand a second piston ring part. In a further embodiment, not shown, all piston ringscould also consist of a single part, or all piston ringscould consist of at least two piston ring parts, a first piston ring partand a second piston ring part

The carrier sleeveserves as a holder or carrier for the piston ring devices. As illustratively shown in, the carrier sleevecan have a cylindrical sleeve body. In general, the carrier sleeveis realized as an elongated, sleeve-shaped part that extends between a first end regionand an oppositely located second end region. The carrier sleeve, in particular the sleeve body, has an inner circumferential surfaceand an oppositely oriented outer circumferential surface. The outer circumferential surfacecan, for example, form the lateral surface of a circular cylinder. The inner circumferential surfacecan also form cylindrical areas. Furthermore, the inner circumferential surfacecan, for example, have or form steps, which in each case delimit cylindrical areas in relation to the longitudinal axis L, as illustratively shown in.

Optionally, the carrier sleevecan have a collarat one axial end, e.g. at the end of the sleeve body, e.g. at the end to which the first end regionis connected. As illustratively shown in, the collarprotrudes vertically from the outer circumferential surfaceof the sleeve body, and thus extends in the radial direction R.

In this preferred embodiment, the carrier sleevealso has a mechanical interface, which is designed for connecting or attaching a withdrawal tool(). The mechanical interfacecan be realized, for example, as shown in, by a thread that is formed on the carrier sleeve, e.g. at the end of the sleeve body.shows as an example that the mechanical interface is realized as an internal thread, which is formed on the inner circumferential surfaceof the carrier sleeve. As illustratively shown in, the mechanical interfacecan be arranged in the second end areaof the carrier sleeve, regardless of its specific design. In the example shown in, the internal threadis therefore formed in the second end regionof the sleeve body, which faces away from the optional collar. Instead of a thread, the mechanical interfacecan also be designed differently in order to create a connection between the carrier sleeveand the withdrawal toolthat enables the carrier sleeveto be pulled off, e.g. by means of a mechanical interfacewith slots running at right angles in the carrier sleeve, which form part of a bayonet lock with the withdrawal tool, for example.

As shown in, the piston ring devicespreferably each comprise a chamber ringand a piston ring. The chamber ringscan, for example, have an L-shaped cross-section, as illustratively shown in. The piston ringsare held on the chamber ring, in particular on its outer circumference. As shown in, the piston ringscan, for example, be held in a receiving space of the chamber ring, which is formed by the L-shaped cross-section. In general, the piston ringsprotrude beyond the outer circumference of the chamber rings.shows, by way of example, that a first subset of the piston ringsare designed as sealing elements with a rectangular cross-section and a second subset of the piston ringsare designed as sealing elements with a trapezoidal cross-section. However, it is also conceivable that all piston ringsare of the same design. Furthermore, other cross-sectional shapes of the piston ringsare also conceivable and/or that all piston ringshave the same cross-section. It is also possible that several partial piston rings,of a piston ringare held on a chamber ring. As shown in, the piston ring devices, in particular the chamber rings, can each have at least one through hole. Several through holescan be provided along a circumferential direction for each piston ring device, e.g. two, three or four.shows a purely exemplary sectional view in which two through holesper piston ring arrangementare visible.

As illustratively shown in, the piston ring devicesare arranged on the outer circumferential surfaceof the carrier sleeve. In particular, the carrier sleevepasses through a central ring opening of all chamber rings. The piston ring devicesor the chamber ringsare arranged next to each other or on top of each other so that the chamber ringsabut against each other. Optionally, a last chamber ringin relation to the longitudinal axis L rests against the optional collarof the carrier sleeve, as illustratively shown in. As also shown in, the piston ring devicescan be aligned in such a way that the through openings of the chamber ringsare aligned. The piston ring devices, in particular the chamber rings, can for example be frictionally connected to the outer circumferential surfaceof the carrier sleeve, e.g. by the central ring opening of the chamber ringsand the outer circumferential surfaceof the carrier sleeveforming an interference fit.

As illustratively shown in, the piston ring devicescan be clamped between the optional first end pieceand the optional second end piece. As shown in, the first end piececan be arranged in particular in the second end regionof the carrier sleeve, and the second end piececan be arranged in the first end regionof the carrier sleeve, e.g. resting against the optional collarof the carrier sleeve. The first end piececan be formed, for example, by a cover ring which encloses the outer circumferential surfaceof the carrier sleeve. The second end piececan, for example, be formed by a last or outermost chamber, as shown as an example in. However, it is also conceivable that the second end pieceis formed by the optional collarof the carrier sleeveor by a ring element, as described for the first end piece.

As illustratively shown in, the second end piececan have a recesswith an internal thread. Several recessesper end pieceare also conceivable, with the recess(es)being arranged in alignment with the through holesof the chamber rings. For its part, the first end piececan have one or more recesses, which are arranged in alignment with the through holesof the chamber rings. As illustratively shown in, a threaded rodcan be provided, which extends through the recessesof the first end pieceand the through holesof the chamber ringsand is screwed into the internal thread of the respective recessof the second end piece. To axially secure the chamber ringsalong the threaded rodor to generate a clamping force between the first and second end pieces,, a nutcan be screwed onto an end of the threaded rodthat protrudes beyond the first end piece, as illustratively shown in. In general, each piston ring devicecan thus have a through holeand a threaded rodextending through it, which connects the first and second end pieces,to one another. In this way, all piston ring devicescan be connected to one another along the longitudinal axis L.

The piston ring packageis arranged on the circumferential surfaceof the piston rod. As illustratively shown in, the piston rodcan be passed through the recess defined by the inner circumferential surfaceof the carrier sleeve. The piston ring packageis thus arranged on the piston rodin such a way that the carrier sleeveextends along the longitudinal axis L. The inner circumferential surfacefaces the circumferential surfaceof the piston rod. Optionally, for example, it can be provided that the carrier sleeveis frictionally attached to the circumferential surfaceof the piston rod. For example, the inner circumferential surfaceof the carrier sleevein the first end regionof the carrier sleevecan bear against the first axialsection of the circumferential surfaceon the piston rod, as illustratively shown in. In general, the inner circumferential surfaceof the carrier sleevecan at least partially abut the circumferential surfaceof the piston rod. In general, the carrier sleeveis thus releasably attached to the piston rod. As can also be seen in, the inner circumferential surfacein the second end regionof the carrier sleevecan be located in the radial direction R at a distance from the second axial sectionof the circumferential surfaceof the piston rod. This allows an annular gap to be formed in the second end regionof the carrier sleevebetween the inner circumferential surfaceof the carrier sleeveand the circumferential surfaceof the piston rod. This facilitates the accessibility of the mechanical interface, for example in the form of an internal thread.

As further shown in, it can be provided that the optional collarof the carrier sleeverests against the shoulderof the piston rod. The second end regionof the carrier sleeve, in which the mechanical interfaceis preferably arranged, can, for example, be located facing the expansion sectionof the piston rod.

The guide ringof the pistonis used for contact with an inner surface of a cylinder of the compressor (not shown). As shown in, the pistoncomprises an upper piston part, on which the guide ringand an optional piston ringare arranged. The upper piston parthas a cylindrical outer circumferential surfaceand an inner circumferential surfacewhich is oriented in the opposite direction thereto. Recesses can be provided on the outer circumferential surface, in which guide elements or a guide ringare arranged. As can be seen in, the guide ringcan have a trapezoidal circumference, for example. The inner circumferential surfacedefines a central passage extending in the longitudinal direction L between two opposing end faces of the upper part of the piston. As illustratively shown in, a centering collarcan be formed on a first end face, which surrounds the passage. A recess, which laterally surrounds the passageway, can be formed on an opposite second end face, as illustratively shown in.

The piston rodcan be passed through the passage of the piston top sectiondefined by the inner circumferential surface, as shown in. The centering collarcan optionally be inserted into the carrier sleeveand lie against the inner circumferential surfaceof the carrier sleeve. Advantageously, the first end face of the piston top sectioncan rest against the piston ring package, e.g. against the carrier sleeveand/or the first end piece, as shown in. An end of the optional threaded rodprojecting from the piston ring packageand the nut, if provided, can be accommodated in corresponding recessesof the first end face of the piston top section.

The optional axial lockcan, for example, have a ringwith an internal threadand several through holes. The ringcan be screwed with its internal threadto an optional piston rod thread, which can be provided in the end region of the piston rod. The ringcan also be clamped to the piston top sectionvia fastening meansarranged in the through holes, and advantageously via a spacer washer, thereby securing it. In this way, an axial force is applied to the carrier sleevevia the piston top sectionby the axial lockor the piston ring packageis clamped between the axial lockand the collar. In principle, it is also conceivable that the axial lockpresses directly onto one end of the carrier sleeve.

As illustratively shown in, the ringcan be arranged in the recessof the upper part of the piston. Optionally, a spacer diskcan be arranged between the base of the recessand the ringin relation to the longitudinal axis L, as illustratively shown in. Furthermore, the through holesof the ringcan be provided with internal threads into which screwsare screwed so that they press against the spacer diskor directly against the base of the recess

illustratively shows another pistonin a sectional view. The pistonshown indiffers from the piston shown inin that the piston ring devicesare not connected to each other by a threaded rod, but are clamped between the first and second end pieces,by a force exerted by the piston top sectionand the axial lock. In particular, the first end face of the upper piston partis in contact with the second end piece, so that the piston ring devicesare clamped between the upper piston partand the collarof the carrier sleeve. In this way, the piston ring devicescan be connected to each other along the longitudinal axis L or held securely against each other.

shows an example of a withdrawal toolfor removing the piston. As illustratively shown in, the withdrawal toolcan have a coupling devicefor attachment to the preferred mechanical interfaceof the carrier sleeveand a pulling devicefor applying a force F directed along the longitudinal axis L to the coupling device.

The coupling devicecan, for example, have a sleeveand an end plate. As illustratively shown in, the sleevecan define an open receiving space, which can be cylindrical, for example. A connecting structure, e.g. in the form of a thread, can be formed at a first end section of the sleeve, which is designed for connection to the preferred mechanical interfaceof the carrier sleeveof the piston ring pack.shows by way of example that the connecting structurecan, for example, be designed as an external thread.

The end plateis connected to the sleeve. For example, the sleeveand the end platecan be formed in one piece or as one part. In particular, the end platecan be arranged on a second end section of the sleeveopposite the first end section, as illustratively shown in. The end platecan, for example, have a through holewith an internal thread, as shown in.